Well done you are half way right in saying this but you missed out the skin damage and much late the ulcerations.
capewind was the first to say it now we will because it is imperative you treat your fish sharpish before much more damage is done to them .
When tricodina attacks a fish the skin is how can I say broken by the parasite look at your fish , you see the pink areas well thats what says its Tricodena before it became bare like that it had to be either black white or red but not pink clear skin which you see here it takes a huge infection to cause this type of damage..
Look at the condition of the fish as a whole and how its presenting itself too you tricodena presents as follows Flashing flicking and rubbing as they try to releave themselves the irritation caused by the parasite .
This behavour can lead to Pysical damage which in turn leads to secondary ifection from bacteria and fungus..
Other than all of the above the fish will start to float just bellow the surface some will seem emaciated i;e looking as though its body is too large for the fish,thekoi will also develope a whitish appearance especially around the head area,in worst case senario the fish will become totally covered in this exess mucus it may start to shake its head vary rapidly from side to side as if it was trying to clear some sort of blockage .
With gill infestations the fish becomes very lethargic and weakthey at this stage should be being drawn towards you drain or skimmer.
If left un treated it will kill your fish your going to need PP to treat them beacuse the salt load at 44ib per 220 gallons (.20 kg of salt per 1000 ltrs for between 10 - 20 minutes ({the recomended dose rate) just is going to ruin everything in the pond as thats a heavy load od salt , that the has to be removed ,
thats why PP is the recomended treatment at a dose rate of 1.5g p[er 1,000 ltrs or 22 gallons.
PP is one of the easiest things to buy anywhere come on are you telling me its even banned from Canadian schools ?
However if you dont think its this do your own thing and your fish will die rather quickly but I'm going to remind you of the initial symptoms you presented with if thats ok wayne ...
rgrds
Dave
